The present invention relates to a conveyor and more particularly to a belt driven roller conveyor. The invention can be used with straight or curved roller conveyors.
Conventional roller conveyors are often belt driven either by a plurality of intermediate O-ring belts associated with each of the respective rollers or a single continuous closed loop direct drive belt which extends over a discrete length of the conveyor section. Heretofore, one type of closed loop drive belt that has been used on roller curves has a round cross-section comprising a rubber-covered cord. The round closed loop belts, however, are limited in length. Consequently, the belt drive system configuration is dictated by the available lengths of the belts. Furthermore, because of their geometry, as the round or circular belts are driven in their closed loop, the round belts may twist which over time may cause the belt cords to break. Moreover, due to the conventional configurations of the round belt driven systems, replacement of these belts requires partial disassembly of the conveyor. As a result, the conveyor is removed from production creating xe2x80x9cdown-timesxe2x80x9d. Replacement of these belts, therefore, may impose a significant cost on the user of the conveyor.
In an attempt to reduce the strain on the round closed loop belts, intermediate O-ring drivers have been implemented. The intermediate O-ring drivers drive the rollers with the O-ring drivers being driven by the round belt. However, the round belts still may exhibit short life spans. More recent attempts to solve this problem have been to use link belts instead of continuous round rubber covered cord belts. Replacement of the link belts requires no disassembly of the conveyor per se and, as a result, is relatively quick and simple compared to the continuous round belts. Furthermore, it is suggested that the link belts may have a higher mean time between failures than continuous belts because they use a different internal structure. However, use of link belts has not been without difficulties. The link belts have either a substantially round cross-section or a generally triangular cross-section. Both shapes, however, have an undulating drive surface. The triangular cross-sectioned link belt includes a V-shaped base, with the upper surface comprising the driving surface of the belt. The triangular cross-sectioned belts are driven by V-shaped pulleys which provide lateral restraints on the belt and prevent twisting of the belt. However, the link belt driven systems exhibit significantly increased noise due to the vibration of the belt and other components as the belt""s undulating surface contacts the rollers. The circular cross-section has a non-uniform circumference when certain portions of the belt are in contact with the rollers. The noise can be extreme.
Consequently, there is a need for a belt drive system for a roller conveyor which is relatively simple to service or replace and which exhibits an increased life expectancy without the increased noise associated with the conventional link belts.
The present invention provides a belt driver system for a roller conveyor which exhibits a longer life span than conventional round driver belts and, yet, does not exhibit the increased noise associated with conventional link belts.
According to one form of the invention, a belt for driving one or more rollers on a roller conveyor includes a body having a base and a substantially continuous driving surface for driving the rollers. The base has a non-circular cross-section so that pulleys which support and guide the belt can laterally restrain the belt and minimize twisting of the belt.
In one aspect, the base comprises a generally V-shaped base. In other aspects, the belt comprises a link belt, which is formed by a plurality of interlocking links. The link belt preferably includes tapered portions which are substantially aligned to provide the substantially continuous linear driving surface.
In yet other aspects, the belt includes an axis of symmetry with the driving surface being offset from the axis of symmetry. Preferably, the driving edge is offset from the axis of symmetry by an angle from a range of 55 to 65 degrees.
In another form of the invention, a belt driver system includes a closed loop belt having a non-circular base and a substantially continuous driving surface for driving the rollers of a conveyor. The belt driver system further includes a plurality of pulleys which support the belt and which are constructed and arranged to position and maintain the belt in an orientation in the pulleys. A first group of the pulleys position the belt for contacting the one or more rollers with the driving surface.
In one aspect, at least one of the first group of pulleys includes a lateral restraint for maintaining the belt in the proper orientation in the at least one pulley. The lateral restraint may for example comprise a bearing which is supported adjacent the at least one pulley and which contacts a portion of the driving portion of the belt. In other aspects, one of pulleys comprises a tensioner pulley for maintaining the tension of the belt.
In other forms, the base of the closed loop belt comprises a V-shaped base, with each of the pulleys supporting the belt in a groove commensurate in size with the V-shaped base thereby providing lateral support to the belt.
In yet another form of the invention, a conveyor includes a support frame, a plurality of rollers rotatably supported on the support frame, and a belt driver system. The belt driver system includes a closed loop belt and a plurality of pulleys for supporting and guiding the belt around a closed path on the conveyor. The belt includes a substantially continuous driving surface for driving the rollers. A first group of the pulleys comprises support pulley assemblies, which are angled in a non-orthogonal orientation to the rollers for orienting the belt to engage the rollers with the driving surface. Further, one of the pulleys comprises a slave drive pulley which is constructed and arranged for driving an adjacent conveyor section.
In one aspect, each of the support pulleys includes a bearing which provide lateral restraint for the belt.
In other aspects, the support pulleys are mounted to the frame by spring mounting members which minimize the pressure from the belt on the rollers to reduce wear and tear on the rollers. This also provides for consistent pressure even if there is a variation such as in belt thickness.
In yet another aspect, the frame includes an inner radius frame member and an outer radius frame member forming a curved conveyor section. A first group of the rollers comprising tapered rollers having smaller diameters at the inner radius frame than at the outer radius frame member. The belt is positioned adjacent the inner radius frame member for engaging the smaller diameters of said tapered rollers such that the curved conveyor speed at the small end of the roller is the same as adjacent conveyor sections with straight rollers.
The improved belt and belt driver system provides for increased life of the belt while reducing the noise associated with link belts. These and other advantages will be appreciated from a review of the description of the preferred embodiments in conjunction with the drawings which follow.